One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure.
The change in internal energy of the gas during the transition is
20 kJ
-20 kJ
20 J
20 J
A.
20 kJ
A slab of stone of area of 0.36 m2 and thickness 0.1 m is exposed on the lower surface to steam at 100oC. A block of ice at 0o C rests on the upper surface of the slab. In one hour 4.8 kg of ice is melted. The thermal conductivity of slab is
(Given latent heat of fusion of ice = 3.36 x 105 J Kg-1)
1.24 J/m/s/oC
1.29 J/m/soC
2.05 J/m/so C
2.05 J/m/so C
A.
1.24 J/m/s/oC
The charge following through a resistance R varies with time t as Q = at - bt2, where a and b are positive constants. The total heat produced in R is,
a3R/3b
a3R/2b
a3R/b
a3R/b
D.
a3R/b
Given,
Charge, Q = at - bt2 ... (i)
We know that,
... (ii)
...(iii)
The two ends of a metal rod are maintained at temperatures 100o C and 110o C. The rate of heat flow in the rod is found to be 4.0 J/s. If the ends are maintained at temperatures 200o C and 210o C, the rate of heat flow will be
44.0 J/s
16.8 J/s
8.0 J/s
8.0 J/s
D.
8.0 J/s
Here, Δ T1 = 110-100 = 10o C 
As the rate of heat flow is directly proportional to the temperature difference and the temperature difference in both the cases is same i.e. 10o C. So, the same rate of heat will flow in the second case.
Hence,
Coefficient of linear expansion of brass and steel rods are 
and 
. Lengths of brass and steel rods are l1 and l2 respectively. If (I2 - I1) is maintained same at all temperatures, which one of the following relations holds good?
C.
Coefficient of linear expansion of brass = 
Length of brass and steel rods are l1 and l2 respectively.
Given,
Increase in length (l2'-l1' ) is same for all temperature.
So,
l2'-l1' = l2 - l1
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